(1) Field of the Invention
The present invention relates to underwater propulsion and maneuverability. More particularly, the present invention relates to a subsurface oscillating blade propeller adapted for use on an underwater vehicle.
(2) Description of the Prior Art
There is increasing reliance on underwater vehicles, both manned and unmanned, to perform missions such as underwater reconnaissance and mine detection, hydrographic mapping, and homeland defense missions such as swimmer and vehicle detection and ship hull or structure inspections. A variety of vehicles are employed for these missions. Though some have novel propulsion methods, the vehicles can normally be categorized into two main types, box-type and torpedo-type.
As their name implies, box-type vehicles are normally box shaped and use thrusters fixed in various positions for dynamic control. They may vary in size and are generally used for missions that do not require vehicle speed, but instead require the vehicle to slowly hover in the mission area. Box-type underwater vehicles perform such missions as hull or target inspections and hardware recovery.
Torpedo-type underwater vehicles also vary in size. These vehicles generally use rearward facing propellers to move quickly through the water and are hydrodynamically shaped to lessen drag. These vehicles are typically used to cover large areas at speed. Torpedo-type underwater vehicles perform such missions as area reconnaissance and hydrographic mapping using side scan sonar and other sensors.
There are currently efforts to merge the two types of underwater vehicles by integrating fore and aft hover modules on torpedo-type underwater vehicles. Similar to the propulsion method of the box-type vehicles, hover modules consist of fixed thrusters. Each module normally contains a fixed vertical thruster and a fixed horizontal thruster.
The hover module system enables the vehicle to perform limited maneuvers including ascent and descent on a designated vertical plane, translation left and right on a designated horizontal plane, and rotation on a designated horizontal plane. A limitation of the system is that each of these behaviors uses only about 50% of the available thrust. Only one thruster in each module provides the maneuvering thrust with the other providing some small control thrust. To change direction when hovering, the thrusters must come to a stop and reverse direction.
Thus, a need has been recognized in the state of the art to provide systems for maneuvering a torpedo-type underwater vehicle. The systems need to minimally impact the hydrodynamics of the vehicle at high speed, while providing efficient maneuverability at slower speeds. Specifically, the systems need to provide thrust in any direction utilizing the maximum available power. Additionally, dynamic roll control, or stability of the vehicle at both slow maneuvering speeds and high speeds should not be adversely impacted, but should be enhanced.